Internal combustion engines require efficient and reliable seal systems to retain the various working fluids, such as fuel and oil, and other fluids such as air, in their respective chambers and compartments. One particular seal is the annular seal which fits around the rotating drive shaft of the fuel pump drive system and separates the pressurized fuel on the pump side of the shaft from the oil at slightly above atmospheric pressure existing on the drive train side of the shaft. This seal also is intended to retain oil in the engine crank case and to prevent contaminants from entering into the engine from the ambient environment.
Numerous attempts have been made to provide inexpensive and durable seals which exhibit a high degree of structural integrity and durability over long periods of time and which provide effective fuel pump drive shaft seals or seals for use in similar environments. However, historically, such drive shaft seals have been plagued by various design weaknesses.
Frequently, annular shaft seals of this type are formed with two separate and independent seal assemblies, with seals which are typically formed of rubber or a similar synthetic material, to provide additional sealing protection in the event of a failure of one of the assemblies. As a further measure of protection, these seal assemblies may be spaced to form a vent or channel which provides fluid communication from the area between the two seal elements to an external area such as one exposed to atmospheric conditions. U.S. Pat. Nos. 3,190,661 to Wahl et al, 3,575,426 to Durham, 4,153,259 to Torstensson and 4,756,536 to Belcher all disclose such dual sealing assemblies formed to provide a vent or channel between sealing elements.
It is both difficult and time consuming to individually mount and position two separate seal assemblies on a shaft and to then effectively seal each of the individual assemblies against leakage. Also, the open vent or channel between the seals provides an access for seal damaging contaminants which are present in an engine environment. However, for many seal applications, the vent or channel is a necessary component.
Seal assemblies used for fuel pump drive shafts are subjected to high pressure fuel on one side and a low pressure area on the opposite side, and significant variations in the fuel pressure make it difficult to maintain an effective seal. Fuel side pressure spikes often result in seal assembly outer diameter sealant leaks, and excessive pressure spikes can cause seal assembly blowout where the seal assembly is actually dislodged from a seal retaining bore. If blowout is prevented by positively retaining the seal assembly in the bore, such excessive fuel side pressure spikes will destroy the seal assembly.